1. Field of the Invention
The present invention generally relates to dumping, and more particularly to dumping using a limited address space.
2. Description of the Related Art
In a conventional computer system, an I/O (input/output) adapter may fail during runtime triggering a dump of the I/O adapter's internal address space for debugging purposes. More specifically, in response to an I/O adapter failure, the driver of the I/O adapter may cause a processor in the computer system to read the entire internal address space of the failed I/O adapter into a temporary buffer in system memory. In other cases, the driver may not anticipate the failure and, as a result, the system hangs. In such cases, the system operator can, via special hardware, cause the processor to read the dump data out of the I/O adapter's internal address space. The processor then stores the read data (dump data) from the temporary buffer into a nonvolatile storage device (usually a hard disk). The process of reading an I/O adapter's internal address space and storing the read data into a nonvolatile storage device is called a dump. Then, the content of the I/O adapter's internal address space is examined to determine the reason for the I/O adapter failure. This examining process is called debugging. The process of storing dump data into a nonvolatile storage device is simple. However, the process of reading an I/O adapter's internal address space is more problematic. This is because there may not be enough system address space for reading all internal address spaces of all I/O adapters in the system during a dump. In addition, the I/O adapter failure may disable the I/O adapter function(s) for providing dump data to the system.
One first prior art method for reading an I/O adapter's internal address space during a dump comprises mapping the I/O adapter's entire internal address space into the system address space. Then, a processor reads from each location of the I/O adapter's internal address space by issuing the system address of the location on the system's address bus. For illustration of this first prior art method, assume an I/O adapter with an internal address space of 1 Mbytes fails to operate during runtime. The I/O adapter's internal address space of 1 Mbytes is mapped into a system address space range of, illustratively, A0000000h-A00FFFFFh (1 Mbyte range) in the system address space. Then, a processor in the system reads from system address A0000000h to access the first byte of the I/O adapter's internal address space, reads from system address A0000001h to access the second byte of the I/O adapter's internal address space, and so on until the last byte of the I/O adapter's internal address space is read.
This first prior art method requires a relatively large portion of system address space (1 Mbytes in the illustration above) for reading the I/O adapter's internal address space, which is problematic. New technologies lead to new I/O adapters with larger internal address spaces (as much as 512 Mbytes or more per I/O adapter). In addition, the number of I/O adapters in the system increases, while the system address space is fixed at 4 Gbytes (assuming a 32-bit system address bus). Assume a dump of all I/O adapters' internal address spaces is required for debugging. Each I/O adapter's internal address space must be mapped into an exclusive system address space range. As a result, if the total internal address space of all I/O adapters in the system exceeds the system address space, there is not enough system address space to map all internal address spaces of all the I/O adapters in the system. This results in a loss of dump data, which is undesirable.
A second prior art method for reading an I/O adapter's internal address space during a dump requires the system to send a dump message to the I/O adapter. The dump message informs the I/O adapter of the area of the I/O adapter's internal address space to be dumped and the system buffer (in system memory) into which the dump data should be sent. In response, the I/O adapter retrieves and sends the requested dump data to the indicated system buffer. In order to do this, the I/O adapter must be capable of (a) generating control signals, addresses, and data on the bus on which it resides and (b) signaling the system when the I/O adapter finishes sending the requested dump data to the indicated system buffer. For example, assume the dump message from the system specifies to the I/O adapter a system buffer at addresses D0000000h-D000FFFFh. In order to send the first byte of dump data, the I/O adapter has to put address D0000000h and the first dump data byte on the bus. In addition, the I/O adapter has to assert one or more control signals to indicate to the system that the address and data on the bus are valid. In other words, the I/O adapter must be able to perform the functions of a bus master. However, the more functions required of an adapter to perform a dump, the more likely that the I/O adapter will be unable to send dump data to the system buffer when the I/O adapter encounters a failure. The reason is that it is likely that the failure disables one of the functions required for the I/O adapter to send dump data to the system buffer. As a result, the second prior art method is also undesirable.
Accordingly, there is a need for an apparatus and method for reading an I/O adapter's internal address space during a dump which overcomes shortcomings existing in the prior art.